% AMP - Non-linear power amplifier%%       usage:[out,inPow,outPow,P3,P_I]=tx_power_amplifier(in,one_dB,G,R,s,N);%             [out,inPow,outPow]=tx_power_amplifier(in,1,1,R,s,N,T);%       % in:     Input data stream% one_dB: Output power at 1 db compression point for amplifier (dBW)% G:      Linear Gain of the amplifier (dB)% R:      Source Impedance% s:      Knee sharpness of limiter% N:      Number of samples in one period for power estimation%% out:    Output data stream% inPow:  Estimate of input power. (dB)% outPow: Estimate of output power (dB)% P3:     Estimate of third order intermod products power (dB)% PI:     Estimate of third order intercept power (dB)function [out,inPow,outPow,P3,P_I]=amp(in,one_dB,G,R,s,N,T);%%  REFERENCES:%%  TARGET: %%  REVISION HISTORY:%    DATE       AUTHOR                  DESCRIPTION                       STR%  02-28-97  John D Terry              Original Code%%*******************************************************************************[r,q]=size(in);if r>q  in=in.';  L=r;else  L=q;endif ~(r == 1 | q == 1)  error('input must be a vector');end%% Compute square of each sample%square=in.*conj(in);%% Group data into integral number of periods for power estimation%integral=reshape(square(1:N*floor(L/N)),N,floor(L/N));%% Compute power estimates%P_est=mean(integral');%% Compute average Input Power%P_avg=10*log10(mean(P_est'))-10*log10(R);inPow=P_avg;if nargin==6   %   % Linear Gain and correction for limiting amplifier's gain   %   G=G+20*log10(.7);   k1=10^(G/20);   %   % Compute coefficient of cubic power needed to meet third order intercept point   %   k3=10^((30*log10(k1)-10*log10(17.33)-one_dB-10*log10(R))/10);   %   % Compute AM/AM modulation distortion for linear region   %   third_order=in*k1-k3*in.^3+1e-38;   %   % Compute AM/AM modulation distortion for linear region   %    if inPow+G > one_dB + 2     g1=10^((G-1)/20);     third_order=g1*in+1e-38;   end   %   % Third order intercept power dBW   %   P_I=10*log10(2/3*k1^3/k3/R);   %   % Third order intermod product power dBW   %   P3=3*P_avg-2*P_I;   %   % Asymptotic output level of limiter   %   LL=10^((one_dB+1)/20)*sqrt(R);   %   % Limiter Output   %   out=LL*sign(third_order)./(1+(.7*LL./abs(third_order)).^s).^inv(s);elseif nargin==7   %   % Asymptotic output level of limiter   %   LL=10^((max(T(:,2))+4)/20)*sqrt(R);   %   % Spline Fit   %   T=((10*ones(size(T))).^(T/10)*R);   PP=spline(T(:,1),(T(:,2)./T(:,1)));   sqr=(conv(ones(1,N)/N,in.*conj(in)));   out=(sqrt(ppval(PP,sqr(N/2:(N/2-1+length(in)))))).*(in+1e-15*max(in));   %   % Limiter Output   %   out=LL*sign(out)./(1+(LL./abs(out)).^s).^inv(s);end%% Estimate Output Power%OP=out.*conj(out);sum_out=reshape(OP(1:N*floor(L/N)),N,floor(L/N));P_nat=mean(sum_out);outPow=10*log10(mean(P_nat))-10*log10(R);